1. Field of the Art
This invention relates to method and apparatus for processing surfaces of substrates such as TFT substrates of liquid crystal display panels or substrates of color filters, semiconductor wafers or the like through a plural number of wet treatments.
2. Prior Art
For instance, in a fabrication process of TFT substrates of liquid crystal display panels, the substrates are processed through various wet treatments including treatments with such liquids developing agent, etching agent and releasing or exfoliation agent in addition to washing and drying treatments. In processing substrates through a series of wet treatments of this nature, it has been well known in the art to apply a treating liquid on a rotating substrate which is mounted and supported on a rotating spindle. In a washing treatment, for example, substrates are subjected to the so-called megasonic shower in which ultrasonically vibrated pure water is showered on each substrate as a wash liquid, which is one of treating liquids as usually used in various stages of substrate processing.
In connection with the wet processing as mentioned above, it has been known in the art to use a single apparatus which is arranged to process substrates through a plural number of wet treatments such as application of a liquid developer and washing or rinsing with pure water, for example, from Japanese Laid-Open Patent Application H7-245466. The substrate processing apparatus by this laid-open application is arranged as shown in FIG. 11.
In FIG. 11, indicated at 1 is a substrate which is fixed in a predetermined position on a holder plate 3 which is supported on a spindle 2. Denoted at 4 is a cup-like housing which is positioned in such a manner as to circumvent the substrate 1 on the spindle 2. Although not shown in the drawing, a liquid developer feed nozzle and a pure water feed nozzle are located over the substrate 1. The just-mentioned liquid developer and pure water feed nozzles can be turned into and out of an operative position over an opening on the upper side of the housing 4 and a receded or standby position away from the top opening of the housing 4.
While holding the developer and pure water feed nozzles in the respective standby positions, the substrate 1 is set in position on the spindle 2 by means of a substrate handling mechanism. Then, the liquid developer feed nozzle is positioned in the operative position vertically in face to face relation with the substrate 1 through the opening on the top side of the housing 4, and a liquid developer is poured onto upper surfaces of the substrate 1 which is put in high speed rotation by the spindle 2. The liquid developer which has been supplied onto the substrate 1 is spread and diffused radially outward along upper surfaces of the substrate 1 under the influence of centrifugal force. As a consequence, the liquid developer is coated on the entire surfaces of the substrate 1 in the form of a thin film of substantially uniform thickness. At this time, excess liquid developer is shaken off from outer peripheral portions of the substrate 1 and scattered in radially outward directions. In a washing or rinsing stage subsequent to the application of a liquid developer, the liquid developer feed nozzle is moved into a receded standby position, and instead the pure water feed nozzle is advanced into the operative position over the opening on the top side of the housing 4. In this washing stage, similarly to the application of a liquid developer, pure water is poured onto upper surface of the substrate 1 from the pure water feed nozzle, letting pure water spread substantially over the entire upper surfaces of the substrate 1 under the influence of centrifugal force for washing the developer-coated surfaces.
In this connection, each one of the liquid developer and pure water, which has been poured onto the substrate 1, is shaken off and scattered radially outward from peripheral regions of the substrate 1, and splashes of the liquid flow down along the inner surfaces of the housing 4 and collected at its bottom for recovering same. In this case, in order to recover the liquid developer and pure water separately, two recovery tanks 5 and 6 are connected to the processor through suction pipes 7 and 8, respectively. The suction pipe 7 is put in operation during application of the liquid developer to recover the excess liquid developer into the tank 5 through the bottom of the housing 4, while the suction pipe 8 is put in operation in the washing stage to recover spent wash liquid into the tank 6.
As mentioned above, the liquid developer which has been supplied onto upper surfaces of the substrate is caused to spread and scatter in radially outward directions under the influence of centrifugal force. At this time, there are possibilities of splashes of outwardly scattered developer liquid getting around onto the lower side of the substrate or mist of the liquid developer depositing on the lower side of the substrate. In the case of TFT substrates, deposition of the developer liquid on the back side of the substrate will result in detrimental defects of the end products. Accordingly, during a treatment with a liquid of this nature, it is a paramount requisite to protect the lower side of each substrate against splashes or mist of the treating liquid. Nevertheless, there have not been known any protective measures which can be effectively applied to a wet process as described above. Besides, in a spin drying stage following a washing treatment, the substrate is dried by putting same in high speed rotation after stopping supply of a wash liquid, but on such occasions difficulties are often experienced in uniformly drying up the entire surfaces of the washed substrate due to difference in circumferential speed between central and peripheral regions of the substrate, in addition to air circulation which is induced within a housing of a processing apparatus toward the center of rotation of the substrate where vacuum pressure is developed as a result of rotation of the substrate, causing floating mist of a treating liquid to deposit on once-dried surfaces of the substrate.